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Junction details for acoustic performance

This article presents junction details appropriate for both light steel and hot-rolled construction between wall and floor elements. For each junction detail type, e.g. separating wall with separating floor, generally only one wall and one floor construction is considered. Due to the range of wall and floor constructions, it is impracticable to include junction details for all the possible combinations. The details that are included show the level of detailing that is required at the junctions and give principles that can be applied to junctions which are not shown. The details are provided for guidance and should not be used for construction unless checked and approved by a competent person such as an acoustic consultant. Light steel frame system suppliers will generally have their own specific junction details that they have developed and that have shown to be satisfactory through on-site testing.

It is important that the junctions are detailed correctly to minimise the transmission of flanking sound.

To reduce flanking sound transmission the following measures are suggested:

Direct contact between the wall lining and floor finish board should be avoided, to reduce vibration transfer. Wall plasterboard linings should be stopped about 5 mm above the floor decking. The gap should be filled with acoustic sealant for light steel separating floors.

Where a separating floor meets an external or party wall, the void within the wall between the studs should be filled with mineral wool to at least 300 mm above and below the separating floor.

A light steel frame inner leaf structure of an external wall should not be continuous across a junction with a separating wall. A physical break should be maintained, and any sheathing board should also be discontinuous at this.

The decking may span in either direction but where decking profiles are at right angles to the walls the voids (above the beam) are filled with profiled mineral wool inserts and caulked with acoustic or flexible sealant.

The gap between the wall boards and the slab is filled with acoustic sealant.

The joints between wall boards and the ceiling boards are sealed with tape or caulked with sealant.

Ceiling and wall boards should not be in direct contact with any steel beams or columns.

The decking may span in either direction but where decking profiles not parallel with the walls the voids (above the beam) are filled with profiled mineral wool inserts and caulked with acoustic or flexible sealant.

The gap between the wall boards and the slab is filled with acoustic sealant.

The joints between wall boards and the ceiling boards are sealed with tape or caulked with sealant.

Ceiling and wall boards should not be in direct contact with any steel beams or columns.

Inner leaf must not be continuous between storeys.

Junction of a shallow composite separating floor with an external cavity wall